Biblion Bible Commentary
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Sarah shall have a son, and Ishmael is heard
Genesis 17:15-27
15 God said to Abraham, “As for Sarai your wife, you shall not call her name Sarai, but her name shall be Sarah. · WEB
The promise is pinned to one woman and a date, Abraham laughs, and the son he already has is blessed but not chosen.
Sarai is renamed too, and she is the only woman in Scripture whose name God changes. She becomes Sarah, princess, and the promise about her is emphatic: I will bless her, and moreover I will give you a son by her. Yes, I will bless her, and she will be a mother of nations. Kings of peoples will come from her.
Until now the promise had specified Abraham's body Genesis 15:4 and left the mother unnamed, which is the gap Sarai's own plan had been designed to fill. That gap is now closed. The child will be hers, and every alternative arrangement is excluded by a sentence.
Abraham's response is one of the most human moments in the book. Then Abraham fell on his face, and laughed, and said in his heart, "Will a child be born to him who is one hundred years old? Will Sarah, who is ninety years old, give birth?"
He is on his face in worship and laughing at the same time. The arithmetic is not disputable and he does the sum aloud in his own head. Nothing in the text rebukes him for it, and he is the man Scripture holds up as the pattern of faith — which suggests that faith in Genesis is compatible with finding the promise ridiculous.
Then the request, and it is the request of a father: Oh that Ishmael might live before you! Abraham has a thirteen-year-old son whom he loves and who has been in the household as the heir apparent for all that time. What he asks for is not a second promise; it is that the boy he already has should count.
God's answer does two things and separates them cleanly. The covenant line is fixed: No, but Sarah, your wife, will bear you a son. You shall call his name Isaac. The refusal is flat, and the name is given in advance — Isaac means he laughs, so the child will carry his father's laugh as a name for life, and Sarah will add hers to it in the next chapter.
And then Ishmael is answered anyway: As for Ishmael, I have heard you. Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly. He will become the father of twelve princes, and I will make him a great nation.
That is a real blessing and it is not a consolation prize. Twelve princes is the same number as Israel's tribes, and the promise of a great nation is the one made to Abraham in chapter twelve. What Ishmael does not receive is the covenant, and the passage is careful to distinguish being blessed by God from being the line through which the promise runs. Not being chosen for something is not the same as being rejected, and this book keeps making the distinction — with Ishmael here, with Esau later, and with Lot before both.
And the date is set: at this set time next year. After twenty-five years of promises without a schedule, there is a deadline.
Abraham's obedience is recorded with a phrase repeated four times in five verses — in the same day. Every male in the household, including a ninety-nine-year-old man and a thirteen-year-old boy, on the day he was told.
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